Fix

Clear the module cache to force Go to re-download dependencies and regenerate checksums. Run the following command to remove the cached module data and then retry your build:

go clean -modcache

This deletes the GOMODCACHE directory (default: ~/go/pkg/mod) and the go.sum file's cached verification data, resolving mismatches caused by corrupted downloads or proxy inconsistencies.

A "checksum mismatch" error means Go's security check failed because the downloaded code doesn't match the recorded fingerprint. Clearing the cache is like throwing away a suspicious package and ordering a fresh one from the store to ensure it hasn't been tampered with.